This invention relates to a new stabilizer composition for enhancing the resistance to deterioration upon heating of vinyl chloride polymers, and to vinyl chloride polymers having enhanced resistance to deterioration in initial color, heat stability and clarity as a result of incorporating therein a stabilizer composition according to this invention.
The voluminous patent and other literature on the stabilization of vinyl chlorde polymers has been recently summarized by M. Minagawa in U.S. Pat. No. 4,134,868 of Jan. 16, 1979: the portion of this patent from column 1 line 13 to column 2 line 4 here incorporated by reference, can be consulted for a recitation of important heat stabilizers found in commercial use and a list of pertinent review articles.
W. Leistner in U.S. Pat. No. 2,564,646 of Aug. 14, 1951 disclosed vinyl chloride polymer compositions containing polyvalent metal carboxylate stabilizers together with an alkyl or aryl phosphite anti-clouding agent, and in U.S. Pat. No. 2,716,092 of Aug. 23, 1955 disclosed the use of hydrocarbon-substituted phenol metal salts in vinyl chloride polymer stabilizers along with metal carboxylates and organic phosphites.
Additional representative disclosures of organic esters of phosphorous acid used in vinyl chloride polymer stabilizers are by F. Hansen in U.S. Pat. No. 2,867,594 of Jan. 6, 1959, J. Darby in U.S. Pat. No. 2,951,052 of Aug. 30, 1960, L. Friedman in U.S. Pat. No. ,3047,608 of July 31, 1962, R. Buckley in U.S. Pat. No. 3,342,767 of Sept. 19, 1967, J. Scullin in U.S. Pat. No. 3,202,622 of Aug. 24, 1965, and T. Sekiguchi in U.S. Pat. No. 4,105,627 of Aug. 8, 1978.
W. Leistner in U.S. Pat. No. 2,997,454 of Aug. 22, 1961 disclosed polyvinyl chloride compositions of excellent initial color stabilized with a combination of an organic triphosphite with a heavy metal fatty acid salt to which there is added a phosphorus compound having at least one hydrogen atom of acidic character. The phosphorus acids in Leistner's compositions are defined by the formula: ##STR1## In this formula, phosphorus has a valence of three or five, the additional two valences being indicated by dotted line bonds. Typical phosphorus acids coming within this general formula are the following: ##STR2##
In the above formulae R.sub.1 and R.sub.2 represent an organic aliphatic, aromatic or nonaromatic alicyclic hydrocarbon or heterocyclic radical having from one to about thirty carbon atoms. R.sub.1 and R.sub.2 in I, II, III(a) and IV may be the same or different.
In the above formulae. R.sub.1 and R.sub.2 represent an organic aliphatic, aromatic or nonaromatic alicyclic hydrocarbon or heterocyclic radical having from one to about thirty carbon atoms. R.sub.1 and R.sub.2 in I, II, III (a) and IV may be the same or different.
R. Kline in U.S. Pat. No. 3,244,661 of Apr. 5, 1966 disclosed triaryl phosphite rubber stabilizers in which each aromatic ring contains one benzyl or alpha-methyl-benzyl substituent and wherein the aromatic rings may each be further substituted with one or more lower alkyl substituents. Kline's triaryl phosphites are represented by the formula ##STR3## in which R is a hydrogen atom or methyl radical and R' and R" are hydrogen or lower alkyl radicals containing from 1 to 5 carbon atoms.
A. Shepard in U.S. Pat. No. 3,281,506 of Oct. 25, 1966 disclosed a class of secondary aryl phosphite antioxidants, stabilizers, and plasticizers which have the general formula ##STR4## wherein R is selected from the group consisting of a hydroxyl and halogen radicals, Y and Y' are organic radicals containing at least four carbon atoms, and Z is selected from the group consisting of hydrogen, a halogen and an organic radical.
The Y and Y' organic radicals are further characterized as alkyl having from 4 to 12 carbon atoms and aralkyl having from 7 to 12 carbon atoms; however, no specific phosphite in which Y or Y' are aralkyl groups is disclosed.
R. Harrington, Jr. in U.S. Pat. No. 3,274,014 of Sept. 20, 1966 disclosed yarn compositions of synthetic fibers having incorporated a small amount of a metal monoalkyl or monoaryl phosphate, metal dialkyl phosphate, metal alkyl phosphonate, metal alkyl (alkyl phosphonate) or metal dialkylphosphite are resistant to ultraviolet light. Examples show among others yarns spun from dopes of modified vinylidene chloride-acrylonitrile copolymer containing zinc diethyl phosphite.
G. Juredine in U.S. Pat. No. 3,284,386 of Nov. 8, 1966 disclosed organic metallophosphite stabilizers for vinyl chloride polymers represented by the formula ##STR5## in which M can be barium, calcium, and strontium and R and R" can be alkyl- groups, cycloaliphatic groups, aryl groups, aralkyl groups, alkaryl groups, and their halo substituted derivatives, R having from 4 to 18 and R" from 3 to 17 carbon atoms.
F. Kujawa in U.S. Pat. No. 3,412,118 of Nov. 19, 1968 disclosed phosphorous acid monoesters of 2,6-disubstituted and 2,4,6-trisubstituted phenols and their metal salts. Kujawa's monoesters have the formula ##STR6## wherein R is selected from the group consisting of hydroxyl and halogen radicals, Y and Y' are organic radicals containing at least four carbon atoms, and Z is selected from the group consisting of hydrogen, halogen, and organic radicals containing at least four carbon atoms.
The metal salts of the primary aryl phosphites of this invention have the formulas: ##STR7## wherein Y and Y' are organic radicals containing at least four carbon atoms, Z is selected from the group consisting of hydrogen, halogen, and organic radicals containing at least four carbon atoms, X is selected from the group consisting of ammonium, substituted ammonium and metals, and n is an integer from 1 to 4 representing the valence of X. Two formulas have been illustrated to show that two forms of primary phosphites are believed to exist. However, Formula A will be used throughout this application as the presently preferred form.
In Kujawa metal salts, the molar ratio of phosphorous acid monoester groups to metal atoms is equal to the valence of the metal, so that for bivalent metals Kujawa teaches only salts in which there are two phosphorous acid monoester groups for each metal atom.
Kujawa points out prior art "primary aryl phosphites, including the corresponding salts, are too unstable to moisture to permit their general usage", while his aryl phosphites and salts are stable. Ouchi Shinko in Japanese patent publication No. 23,061/75 of Aug. 5, 1975 abstracted in Chemical Abstracts 1976, volume 84, no. 18571f, disclosed stabilizer combinations containing a tris (styrenated phenyl) phosphite of the type disclosed by R. Kline and styrenated phenol for polymers such as polyvinyl chloride and polyformaldehyde.